A dielectric resonator in a radio frequency filter is provided, in which a dielectric resonance element is fixed at the center of a housing space formed by a cover and a housing, a guide groove is formed into a bottom of the housing, for allowing the dielectric resonance element to be inserted therein, a metal plate is interposed between the cover and the housing, and a dielectric fixing screw is engaged with the cover at a position corresponding to an upper end portion of the dielectric resonance element by screwing, for fixing the dielectric resonance element by pressing the upper end portion of the dielectric resonance element.